Search results for "Jet"
showing 10 items of 4711 documents
Consistent measurements of alpha(s) from precise oriented event shape distributions
2000
An updated analysis using about 1.5 million events recorded at $\sqrt{s} = M_Z$ with the DELPHI detector in 1994 is presented. Eighteen infrared and collinear safe event shape observables are measured as a function of the polar angle of the thrust axis. The data are compared to theoretical calculations in ${\cal O} (\alpha_s^2)$ including the event orientation. A combined fit of $\alpha_s$ and of the renormalization scale $x_{\mu}$ in $\cal O(\alpha_s^2$) yields an excellent description of the high statistics data. The weighted average from 18 observables including quark mass effects and correlations is $\alpha_s(M_Z^2) = 0.1174 \pm 0.0026$. The final result, derived from the jet cone energ…
Search for the Associated Production of the Standard-Model Higgs Boson in the All-Hadronic Channel
2009
We report on a search for the standard-model Higgs boson in pp collisions at s=1.96 TeV using an integrated luminosity of 2.0 fb(-1). We look for production of the Higgs boson decaying to a pair of bottom quarks in association with a vector boson V (W or Z) decaying to quarks, resulting in a four-jet final state. Two of the jets are required to have secondary vertices consistent with B-hadron decays. We set the first 95% confidence level upper limit on the VH production cross section with V(-> qq/qq('))H(-> bb) decay for Higgs boson masses of 100-150 GeV/c(2) using data from run II at the Fermilab Tevatron. For m(H)=120 GeV/c(2), we exclude cross sections larger than 38 times the standard-m…
Search for a Fourth Generationt′Quark inpp¯Collisions ats=1.96 TeV
2011
We present a search for pair production of a fourth generation t' quark and its antiparticle, followed by their decays to a W boson and a jet, based on an integrated luminosity of 5.3/fb of proton-antiproton collisions at sqrt{s}=1.96 TeV collected by the D0 Collaboration at the Fermilab Tevatron Collider. We set upper limits on the t't'bar production cross section that exclude at the 95% C.L. a t' quark that decays exclusively to W+jet with a mass below 285 GeV. We observe a small excess in the muon+jets channel which reduces the mass range excluded compared to the expected limit of 320 GeV in the absence of a signal.
Search for new particles in the two-jet decay channel with the DØ detector
2016
We present the results of a search for the production of new particles decaying into two jets in pp collisions at √s = 1.8 TeV, using the DØ 1992-1995 data set corresponding to 109 pb-1. We exclude at the 95% confidence level the production of excited quarks (q*) with masses below 775 GeV/c2, the most restrictive limit to date. We also exclude standard-model-like W′ (Z′) bosons with masses between 300 and 800 GeV/c2 (400 and 640 GeV/c2). A. W√ boson with mass <786 GeV/c2 has been excluded by previous measurements, and our lower limit is therefore the most stringent to date. © 2004 The American Physical Society.
Subjet multiplicity of gluon and quark jets reconstructed with thek⊥algorithm inpp¯collisions
2002
The D empty set Collaboration has studied for the first time the properties of hadron-collider jets reconstructed with a successive-combination algorithm based on relative transverse momenta (k(perpendicular to)) of energy clusters. Using the standard value D = 1.0 of the jet-separation parameter in the k(perpendicular to) algorithm, we find that the p(T) of such jets is higher than the E-T of matched jets reconstructed with cones of radius R = 0.7, by about 5 (8) GeV at p(T) approximate to90 (240) GeV. To examine internal jet structure, the k(perpendicular to) algorithm is applied within D = 0.5 jets to resolve any subjets. The multiplicity of subjets in jet samples at roots = 1800 GeV and…
Heavy quark mass effects in e+e− into three jets
1998
Next-to-leading order calculation for three jet heavy quark production in e^+e^- collisions, including complete quark mass effects, is reviewed. Its applications at LEP/SLC are also discussed.
Measurement of color flow intt¯events frompp¯collisions ats=1.96 TeV
2011
We present the first measurement of the color representation of the hadronically decaying W boson in t-tbar events, from 5.3 fb^-1 of integrated luminosity collected with the D0 experiment. A novel calorimeter-based vectorial variable, "jet pull," is used, sensitive to the color-flow structure of the final state. We find that the fraction of uncolored W bosons is 0.56 +- 0.42(stat+syst), in agreement with the standard model.
From RHIC to LHC
2007
Measurements of the nuclear modification factor of inclusive yields of $\pi^0$, $p\bar{p}$, non-phtonic electrons and prompt photon measured at RHIC are reviewed. Some of the difficulties arising from interpretation of these measurements such as similarity of the suppression pattern of light and heavy quarks, quarks and gluons, light quarks and prompt photon are discussed. The potential of two-particle and promt photon correlation technique to unravel some of these open questions is presented. An emphasis is given to the influence of partonic transverse momentum on the prompt-photon correlations. The smearing between the trigger photon and back-to-back jet at LHC energy is discussed.
Measurement of the top quark mass in the lepton+jets channel using the ideogram method
2007
A measurement of the top quark mass using events with one charged lepton, missing transverse energy, and jets in the final state, collected by the D0 detector from p-pbar collisions at sqrt{s} = 1.96 TeV at the Fermilab Tevatron collider, is presented. A constrained fit is used to fully reconstruct the kinematics of the events. For every event a top quark mass likelihood is calculated taking into account all possible jet assignments and the probability that an event is signal or background. Lifetime-based identification of b jets is employed to enhance the separation between t-tbar signal and background from other physics processes and to improve the assignment of the observed jets to the q…
Three-Loop Quark Jet Function.
2018
We calculate the massless quark jet function to three-loop order. The quark jet function is a universal ingredient in SCET factorization for many collider and decay processes with quark initiated final state jets. Our three-loop result contributes to the resummation for observables probing the invariant mass of final state quark jets at primed next-to-next-to-next-to-leading-logarithmic accuracy. It represents the first complete three-loop result for a factorization ingredient describing collinear radiation. Furthermore it constitutes a major component of the N-jettiness subtraction method at next-to-next-to-next-to-leading order accuracy, which eventually may enable the calculation of full…